ABC, CBS and NBC stop the service from accessing full-length episodes of their prime-time shows. They worry that to do otherwise would undercut the economics that support the industry.

The three major broadcast networks, uneasy about viewers bypassing cable and satellite providers — and the networks' own websites — to watch their TV shows, have begun blocking a new service from Google Inc. that is designed to make it easy for people to watch programming online.

ABC, CBS and NBC confirmed that this week, they began blocking Google TV from accessing full-length episodes of prime-time shows such as "NCIS: Los Angeles," "Dancing With the Stars" and "Parks & Recreation," a move aimed at forestalling the technology giant's entry into the living room.

Google TV seeks to marry the Internet with television by allowing viewers to search the Web for shows and then watch them on their TV sets. The technology is designed to make it easier for people to watch TV shows when they want, rather than be at the mercy of network schedules or sift through the Web to find shows on the networks' own websites.

But the networks worry that providing consumers with direct access — via the Internet — to popular shows would undercut the economics that support the industry. The networks fear, among other things, that Google TV could disrupt advertising and encourage people to discontinue their cable TV service. Cable providers pay billions in fees to carry the programming of the networks' co-owned cable channels.

Others have cited fears that Google TV would fuel piracy by letting viewers access bootleg streams of TV shows on the Internet.

"Google TV enables access to all the Web content you already get today on your phone and PC," Google said in a statement. "But it is ultimately the content owner's choice to restrict their fans from accessing their content on the platform."

Google continues to pursue talks with the networks. It also is in discussions with Hulu about bringing the Hulu Plus subscription service to the platform — which would give Google TV users access to full-length episodes of shows from ABC, Fox and NBC.

Forrester Research analyst James McQuivey said that blocking access to network shows on Google TV wouldn't prevent people from watching the shows online because simple workarounds, such as hooking up a laptop to the TV set, can accomplish the same thing.

Some content providers have sought to work with Google. Time Warner Inc. plans to offer HBO Go — which allows people who already pay for HBO on cable or satellite to watch shows online — through Google TV.

Time Warner executives say cable operators historically have done a poor job helping viewers navigate hundreds of channels of TV shows or movies. Google TV could fill that niche by expeditiously producing a list of sites where viewers could see their favorite shows.